Multipurpose lubricant based on phosphorous and sulphur compounds

ABSTRACT

The multifunctional lubricant according to the invention comprises at least one phosphoric ester (A) of general formula:  
                 
 
     in which k is equal to 2 or 3, m is a number ranging from 0 to 8, x is equal to 1 or 2 and R represents a linear alkyl or alkenyl radical having from 10 to 20 carbon atoms, or a salt of such an ester and at least one polysulphide (B) of general formula:  
     R′—S y —R′ 
     in which y is a number ranging from 2 to 8 and R′ represents a tert-alkyl radical having from 4 to 18 carbon atoms, the A/B ratio by mass being between 0.01/1 and 1/1.

DESCRIPTION

[0001] The present invention relates to the field of lubricants and moreparticularly that of additives which can be used in industrial lubricantformulations for gearboxes, gearings, bearings, compressors, turbines,hydraulic fluids, and the like, or in lubricant formulations for theworking or shaping of metals.

[0002] Lubricant additives are generally classified into three mainfamilies. The boundary additives or lubricity agents, which aregenerally compounds comprising a fatty chain and a polar group (forexample fatty acids), make possible lubrication under conditions of lowload; they form a monomolecular covering on the surface to be lubricatedand thus reduce friction and wear. When the frictional conditions becomemore severe, the rise in the temperature results in a desorption ofthese so-called boundary or lubricity additives, and antiwear (AW) orextreme pressure (EP) additives are then necessary to lubricate thecontact. AW and EP additives are generally compounds comprisingphosphorus, chlorine or sulphur. Under high loads, AW additives make itpossible to greatly reduce the wear of the components in contact; EPadditives can generate a degree of wear but they prevent the phenomenaof welding and of adhesion. An efficient lubricating formulation mustcomprise additives which make it possible to lubricate under the threesystems: boundary, AW and EP; this is then termed a multifunctionallubricant.

[0003] Up until the 1990s, chlorinated paraffins were widely usedbecause of their AW and EP spectrum but their use is tending to begreatly reduced for reasons of toxicity.

[0004] Sulphur compounds, such as, for example, polysulphides,sulphurized olefins or sulphurized fatty substances, have been used fora long time for their EP capability; they make it possible to lubricateunder conditions of high load and/or of high temperatures. The use ofsulphur compounds alone introduces good EP properties but the weargenerated is too great. In addition, numerous sulphur derivatives arenot suitable for the lubrication of yellow metals (copper, copperalloys, and the like) because of their corrosive effect.

[0005] The AW action of phosphorus derivatives is well known. They aregenerally phosphites or phosphoric esters (either triesters obtained byreaction of an alcohol with PCl₃ or mixtures of mono- and diestersobtained by reaction of an alcohol with P₂O₅). The use of phosphoruscompounds alone results in a strong reduction in wear but it does notmake it possible to achieve systems where the frictional conditions arevery severe.

[0006] The combined use of sulphur and phosphorus compounds has alreadybeen recommended in Patents U.S. Pat. No. 3,933,658, DE 2,752,218 and JP54-154405; it makes it possible to obtain a lubricant with AW and EPproperties. However, these compositions are generally not lubricious, somuch so that the addition of fatty substances is necessary in order toavoid stick-slip phenomena and to reduce friction under conditions oflow loads and/or temperatures. In addition, compositions based onphosphorus and sulphur compounds often cause problems of corrosion onyellow metals because of the presence of the sulphur compound.

[0007] It is now been found that the combination of a phosphoric acidester on an ethoxylated or nonethoxylated linear fatty alcohol base andof a di-tert-alkyl polysulphide makes it possible to obtain excellentmultifunctional lubricants (boundary, AW and EP) which, in the case ofpolysulphides lacking free sulphur (ASTM Standard D-1662), prevent thecorrosion of yellow metals.

[0008] A subject-matter of the present invention is therefore amultifunctional lubricant comprising at least one phosphorus compound(A) and at least one sulphur compound (B), characterized in that thecompound A is a phosphoric ester of general formula:

[0009] in which k is equal to 2 or 3, m is a number ranging from 0 to 8,x is equal to 1 or 2 and R represents a linear alkyl or alkenyl radicalhaving from 10 to 20 carbon atoms, or a salt of such an ester and thecompound B is a polysulphide of general formula:

R′—S_(y)—R′

[0010] in which y is a number ranging from 2 to 8 and R′ represents atert-alkyl radical having from 4 to 18 carbon atoms, the A/B ratio bymass being between 0.01/1 and 1/1, preferably between 0.05/1 and 0.4/1.

[0011] Another subject-matter of the invention is an additive formultifunctional lubricants composed of the mixture of at least onephosphoric ester (A) as defined above or a salt of such an ester and ofat least one polysulphide (B) as defined above in an A/B ratio by massof between 0.01/1 and 1/1, preferably between 0.05/1 and 0.4/1.

[0012] Preference is given, among the phosphoric esters (A), to those inwhich k is equal to 2, m is between 2 and 6 and R is a radicalcomprising from 12 to 18 carbon atoms, more particularly the lauryl,stearyl, oleyl or linoleyl radical. The phosphoric esters (A), which aregenerally mixtures of mono- and diesters in proportions ranging from10/90 to 90/10, can be used in the acidic form or in the form of alkalimetal, ammonium or alkanolamine salts.

[0013] Preference is given, among the polysulphides (B), to those inwhich the number y is between 3 and 5 and the R′ radical comprises from4 to 12 carbon atoms. Di-tert-butyl trisulphide, di-tert-nonylpentasulphide, di-tert-dodecyl trisulphide and di-tert-dodecylpentasulphide are more particularly preferred.

[0014] The additive according to the invention can be prepared by simplemixing of the compounds (A) and (B), which are generally liquid at roomtemperature. In some cases, the operation may be facilitated by heating.

[0015] The multifunctional lubricants according to the invention can beobtained by incorporation of the additive according to the invention inwhole oils or in soluble oils (emulsions and microemulsions) in aproportion of 1 to 100 parts of additive (preferably 2 to 50 and moreparticularly 5 to 20) per 100 parts of oil. The oils can be mineral orsynthetic or of animal or vegetable origin and can comprise additivesconventionally used in lubricants, such as, for example, lubricityagents, corrosion inhibitors, emulsifiers, alkaline agents and the like.

EXAMPLES

[0016] In the following examples, which illustrate the invention withoutlimiting it, the parts and percentages shown are expressed by weight.The names and the chemical natures of the compounds used in theseexamples are specified in the following Table 1. TABLE 1 Type of productName Chemical nature Mineral oil 100NSO3 Paraffin oil, 100 NeutralPhosphorus Beycostat A684 Phosphoric ester of oleyl compounds alcoholcomprising 4.5 EO* Beycostat A244 Phosphoric ester of lauryl alcoholcomprising 4 EO Beycostat AB04 Phosphoric ester of nonyl- phenolcomprising 4 EO Beycostat A136 Phosphoric ester of isotri- decyl alcoholcomprising 6 EO Beycostat A130 Phosphoric ester of iso-tridecyl alcoholBeycostat A081 Phosphoric ester of ethylhexanol Sulphur TPS 20Di-tert-dodecyl trisulphide compounds TPS 32 Di-tert-dodecylpentasulphide TPS 37 Di-tert-nonyl pentasulphide TPS 44 Di-tert-butyltrisulphide

[0017] The phosphoric esters which are sold by the Applicant Company arepredominantly composed of monoesters. The polysulphides TPS 20, TPS 32,TPS 37 and TPS 44 are sold by the Company ATOFINA.

[0018] The performances of the lubricants were evaluated according tothe following experimental procedures:

[0019] 1. 4-ball extreme pressure test (ASTM D-2783):

[0020] Evaluation of the antiwear capability by the highest possiblevalue of the load before seizing up (typically >100 kg) and of theextreme pressure capability by the highest possible value of the weldingload (typically >315 kg).

[0021] Conditions: 1500 rev/min, increasing loads for 10 seconds.

[0022] 2. 4-ball wear test (ASTM D-4172):

[0023] Evaluation of the antiwear capability by the lowest possiblevalue of the wear scar (typically <0.60 mm).

[0024] Conditions: 1500 rev/min, 40 kg, 3600 seconds, 75° C.

[0025] 3. Ball-disc test:

[0026] Evaluation of the lubricity or boundary capability of a lubricantby the value of the coefficient of friction μ, which must be as low aspossible, typically <0.05.

[0027] The ball-disc test consists in rotating a disc at a constantspeed under a ball to which is applied a constant load. The disc and theball are immersed in the lubricant. A force sensor measures thecoefficient of friction of the ball-disc lubricated contact.

[0028] Conditions: 1 rev/min, 1 kg, 30 min, 100C6 steel ball on analuminium 3104 disc.

[0029] 4. Corrosion-resistant properties with regard to a copper strip(ASTM D-130):

[0030] As sulphur additives have a tendency to corrode yellow metalsbecause of the presence of free sulphur, this test evaluates thecorrosiveness of the formulations with regard to a copper strip.

[0031] The test consists in immersing a polished copper plate in a testtube comprising 30 ml of formulation for 24 h at 60° C. At the end ofthe test period, the plate is suitably washed and compared withreference corroded strips (the classification ranging from 1a for theleast corroded to 4c for the most corroded).

[0032] 27 additive compositions prepared from the products in Table 1are summarized in the following Table 2.

[0033] Only the compositions 6 to 15 and 17 are in accordance with thepresent invention. The others do not comprise phosphorus compound(compositions 1 to 4) or do not comprise sulphur compound (compositions5, 16, 18, 20, 22 and 24) or comprise a phosphorus compound derived froma nonlinear alcohol (compositions 19, 21, 23, and 25 to 27). TABLE 2Sulphur compound Phosphorus compound Composition Amount Amount numberName (parts) Name (parts) 1 TPS 20 100 none 0 2 TPS 32 100 none 0 3 TPS37 100 none 0 4 TPS 44 100 none 0 5 none 0 Beycostat A684 100 6 TPS 20100 Beycostat A684 5 7 TPS 20 100 Beycostat A684 10 8 TPS 20 100Beycostat A684 20 9 TPS 20 100 Beycostat A684 40 10 TPS 32 100 BeycostatA684 5 11 TPS 32 100 Beycostat A684 10 12 TPS 32 100 Beycostat A684 2013 TPS 32 100 Beycostat A684 40 14 TPS 37 100 Beycostat A684 5 15 TPS 44100 Beycostat A684 5 16 none 0 Beycostat A244 100 17 TPS 20 100Beycostat A244 5 18 none 0 Beycostat AB04 100 19 TPS 20 100 BeycostatAB04 5 20 none 0 Beycostat A136 100 21 TPS 20 100 Beycostat A136 5 22none 0 Beycostat A130 100 23 TPS 20 100 Beycostat A130 5 24 none 0Beycostat A081 100 25 TPS 20 100 Beycostat A081 5 26 TPS 20 100Beycostat AB04 40 27 TPS 32 100 Beycostat AB04 40

Examples 1 to 30

[0034] The compositions in Table 2 were diluted in a 100 Neutral wholeparaffin oil and the performances of the formulations thus obtained arecollated in the following Table 3, where the percentage of dilutionindicates the proportion of additive composition in the formulation.TABLE 3 4-ball wear 4-ball EP Ball- Wear Seizing Welding CorrosionExample Compo- Dilution disc diameter load load Copper number sition (%)μ (mm) (kg) (kg) strip 1 —  0% 0.13  1.70 50 26 1b 2 1 10% 0.082 0.78100 400 3b 3 2 10% 0.075 1.10 100 500 4c 4 3 10% 0.087 1.18 100 500 4c 54 10% 0.077 1.11 126 500 3a 6 5 0.5%  0.036 0.43 100 160 1b 7 6 10%0.047 0.47 160 400 1b 8 10 10% 0.046 0.51 126 620 4c 9 14 10% 0.044 0.45200 620 4c 10 15 10% 0.043 0.54 200 620 1b 11 7 10% 0.044 — 160 400 — 127  5% 0.044 — 100 250 — 13 8 10% 0.043 — 126 400 1b 14 8  5% 0.041 — 126250 — 15 9  5% 0.041 — 126 250 — 16 11 10% 0.039 200 500 — 17 11  5%0.041 126 400 — 18 12 10% 0.038 200 500 4c 19 12  5% 0.040 126 250 — 2013  5% 0.038 126 400 — 21 16  2% — 100 250 — 22 17 10% 0.045 160 400 —23 18  2% — 126 200 — 24 19 10% 0.070 160 400 — 25 20  2% — 126 200 — 2621 10% 0.062 160 400 — 27 22  2% — 100 200 — 28 23 10% 0.074 126 315 —29 24  2% — 100 250 — 30 25 10% 0.103 126 250 —

[0035] On examination of the results in Table 3, it is found that thechoice of the phosphoric ester is determining, since the lubricants ofExamples 24, 26, 28 and 30, comprising an ester not in accordance withthe invention, exhibit a high coefficient of friction (>0.05) and thus alack of lubricity. In addition, it is observed (Examples 7, 10 and 13)that there is inhibition of the corrosion with regard to yellow metalswhen the polysulphide does not comprise free sulphur.

Examples 31 to 39

[0036] Nine lubricants, the performances of which are collated in thefollowing Table 4, were prepared by dispersion in water of the additivecompositions 5, 7, 9, 12, 13, 16, 18, 26 and 27 in Table 2.

[0037] Examples 31 to 33 correspond to the phosphorus compounds alonedispersed in water. Examples 34 to 37 are in accordance with theinvention. Examples 38 and 39 are not in accordance with the invention.TABLE 4 4-ball EP Ball- Seizing Welding Example Dilution disc load loadnumber Composition (%) μ (kg) (kg) 31 5 2% 0.033 80 160 32 16 2% 0.038100 160 33 18 2% 0.064 100 160 34 7 10% 0.050 200 400 35 9 5% 0.043 160315 36 12 5% 0.044 200 315 37 13 5% 0.039 160 315 38 26 5% 0.081 160 20039 27 5% 0.072 200 250

Examples 40 to 44

[0038] A non-additivated microemulsion (Example 40) was prepared with 5%of 100 Neutral paraffin oil, 9.5% of polyethoxylated (4 EO) laurylalcohol, 0.5% of sodium dodecylbenzenesulphonate and 85% of water.

[0039] The additive composition 1, 2, 5 or 7 in Table 2 was subsequentlyadded to samples of this microemulsion and the mixture was heated at 50°C. for homogenization.

[0040] The performances of the lubricants thus obtained, which aretranslucent at room temperature, are collated in the following Table 5.TABLE 5 4-ball EP Ball- Seizing Welding Example Dilution disc load loadnumber Composition (%) μ (kg) (kg) 40 none 0% 0.218 40 126 41 1 5% 0.14663 200 42 2 5% 0.212 63 200 43 5 2% 0.045 80 160 44 7 10% 0.050 126 315

1. Multifunctional lubricant comprising at least one phosphorus compound(A) and at least one sulphur compound (B), characterized in that thecompound A is a phosphoric ester of general formula:

in which k is equal to 2 or 3, m is a number ranging from 0 to 8, x isequal to 1 or 2 and R represents a linear alkyl or alkenyl radicalhaving from 10 to 20 carbon atoms, or a salt of such an ester and thecompound B is a polysulphide of general formula: R′—S_(y)—R′ in which yis a number ranging from 2 to 8 and R′ represents a tert-alkyl radicalhaving from 4 to 18 carbon atoms, the a/b ratio by mass being between0.01/1 and 1/1.
 2. Lubricant according to claim 1, in which k is equalto 2, m is a number ranging from 2 to 6 and R is a radical having from12 to 18 carbon atoms.
 3. Lubricant according to claim 1 or 2, in whichthe number y is between 3 and 5 and R′ is a tert-alkyl radical havingfrom 4 to 12 carbon atoms.
 4. Lubricant according to one of claims 1 to3, in which the A/B ratio by mass is between 0.05/1 and 0.4/1. 5.Lubricant according to one of claims 1 to 4, in which the compound A isa mixture of phosphoric mono- and diesters, the number k being equal to2, the number m being between 4 and 5 and R being the lauryl, stearyl,oleyl or linoleyl radical.
 6. Lubricant according to one of claims 1 to5, in which the compound B is di-tert-butyl trisulphide, di-tert-nonylpentasulphide, di-tert-dodecyl trisulphide or di-tert-dodecylpentasulphide.
 7. Multifunctional lubricant additive, characterized inthat it comprises at least one phosphoric ester (A) of general formula:

in which k is equal to 2 or 3, m is a number ranging from 0 to 8, x isequal to 1 or 2 and R represents a linear alkyl or alkenyl radicalhaving from 10 to 20 carbon atoms, or a salt of such an ester and atleast one polysulphide (B) of general formula: R′—S_(y)—R′ in which y isa number ranging from 2 to 8 and R′ represents a tert-alkyl radicalhaving from 4 to 18 carbon atoms, the A/B ratio by mass being between0.01/1 and 1/1.
 8. Additive according to claim 7, in which k is equal to2, m is a number ranging from 2 to 6 and R is a radical having from 12to 18 carbon atoms.
 9. Additive according to claim 7 or 8, in which thenumber y is between 3 and 5 and R′ is a tert-alkyl radical having from 4to 12 carbon atoms.
 10. Additive according to one of claims 7 to 9, inwhich the A/B ratio by mass is between 0.05/1 and 0.4/1.
 11. Additiveaccording to one of claims 7 to 10, in which the compound A is a mixtureof phosphoric mono- and diesters, the number k being equal to 2, thenumber m being between 4 and 5 and R being the lauryl, stearyl, oleyl orlinoleyl radical.
 12. Additive according to one of claims 7 to 11, inwhich the compound B is di-tert-butyl trisulphide, di-tert-nonylpentasulphide, di-tert-dodecyl trisulphide or di-tert-dodecylpentasulphide.